In order to prevent collisions with other aircraft, a variety of lights are mounted on the exterior of an aircraft in order to indicate its relative position to the other aircraft in the same general airspace. Such lighting systems include a forward position lighting system comprised of a red light mounted on the port wing and a green light on the starboard wing. Based on the color and movement of the forward position lights on an observed aircraft, the relative position and direction of travel of the aircraft is discernable by other aircraft operating in the same vicinity.
Federal Aviation Regulations (FARs) specify minimum and maximum light intensities for each of the red and green forward position lights as a function of the angle of emission. The limitations for maximum intensities, known as “angular cut-offs,” are necessary to prevent excess overlap between these position lights so that other aircraft in the same general airspace can accurately discern between the individual position lights of an aircraft. This assists the other aircraft in determining the relative position of the lighted aircraft. Traditionally, forward position lighting systems have utilized incandescent lamps as a light source. These systems suffer from several disadvantages. Due to their principles of operation, incandescent lamps have a limited life compared to other light sources (e.g., fluorescent, solid-state, and high intensity discharge lights). The harsh environment under which an aircraft operates can further reduce the life of incandescent lamps. Since aviation safety regulations require that the aircraft's position lights be functioning when the aircraft is operating at night, the frequent failures of incandescent positioning lights may result in delayed flight departures as well as high maintenance costs due to replacement.
Furthermore, incandescent-based lighting systems require colored glass filters to achieve the specified colors. Few suppliers worldwide can provide colored glass capable of withstanding the high temperature gradients experienced during operation, while maintaining the FAR-specified colors. Also, this type of glass is very heavy, thereby reducing flight efficiency.
Some existing position lighting systems utilize light emitting diodes (LEDs). However, such systems are not suitable as a direct replacement (either in form or fit) for existing incandescent lights. Thus, some level of “retrofitting” is required in order to install these lights on an aircraft.
In addition, known LED-based position lights have been designed as point solutions—not as a common solution suitable for various platforms. Also, these lighting systems require clusters of LEDs in order to meet the FAR requirements. Another problem associated with known LED-based position lights is the variations in photometric distributions associated with LEDs. Such variations can prevent the position lights from achieving the minimum or maximum intensity distributions required by FARs.